Point source radiating elements such as, for example, patch antennas are well known in the art. In some applications, it is desirable to arrange a plurality of point source radiating elements into an array. As an example, point source radiating elements can be arranged in a ring-shaped array to form an omnidirectional antenna. However, when multiple radiating elements are placed in an array, constructive and destructive interference affects the radiation pattern generated by the array.
In Prior Art FIG. 1, a ring-shaped array 100 of patch antennas, typically shown as 102, generates a specific radiation pattern 104. Radiation pattern 104 indicates the outermost distance from the center of ring-shaped array 100 to which radiation having a specific power level extends. For example, pattern 104 represents the outermost distance from the center of ring-shaped array 100 at which radiation having a power level of 10 dB can be detected. As shown in Prior Art FIG. 1, radiation pattern 104 is not uniform about the center of ring-shaped array 100. Points P.sub.1 and P.sub.2 represent receivers having the ability to receive radiation having a power level of 10 dB or greater. In Prior Art FIG. 1, points P.sub.1 and P.sub.2 are equidistant from the center of ring-shaped array 100. In the example of Prior Art FIG. 1, a receiver located at point P.sub.1 is able to receive radiation transmitted by ring-shaped array 100, while a receiver at point P.sub.2 is outside of the range to which radiation having power level of 10 dB or greater is transmitted. Therefore, a receiver located at point P.sub.2 is not able to receive radiation transmitted by ring-shaped array 100. Thus, even though points P.sub.1 and P.sub.2 are equidistant from the center of ring-shaped array 100, only one of the receivers can communicate with ring-shaped array 100.
The radiation pattern generated by a ring-shaped array differs greatly depending upon various features of the ring-shaped array. Such radiation pattern affecting features include, but are not limited to, the number, location, power and phase distribution, and frequency of each of the patch antennas. Other factors such as the diameter of the ring-shaped array also influence the generated radiation pattern.
In many applications, it is desirable to manipulate the radiation pattern generated by the ring-shaped array. For example, it may be desired to reduce the radiation pattern variation referred to as "ripple." By significantly reducing ripple, the power level of radiation is more uniformly distributed about the periphery of the ring-shaped array. For example, by reducing ripple in the embodiment of Prior Art FIG. 1, both of receivers P.sub.1 and P.sub.2 would be able to receive radiation transmitted from ring-shaped array 100. In one prior art attempt to reduce ripple, changes are made to various constraints of the ring-shaped array. The newly configured ring-shaped array is then experimentally tested to see if desired results are achieved. The experimentation process is continued until the desired results are obtained. Although such an experimental approach can produce a ring-shaped array which complies with desired results, such an approach is labor intensive, time-consuming, and error prone. That is, prior art approaches commonly require repeated construction and testing of the ring-shaped array. Additionally, prior art experimental approach processes do not necessarily determine the minimal number of radiating elements needed in the ring-shaped array to achieve the desired results. That is, an experimentation approach may produce an array which contains more radiating elements than is necessary to achieve desired operating characteristics. As a result, the array includes unnecessary cost, weight, and size.
Thus, a need exists for a method and system which determines the required placement of radiating elements about an array in order to achieve desired operating characteristics wherein the method and system does not require repeated experimentation. A further need exists for a method and system which determines the minimum number of radiating elements required to achieve desired operating characteristics for various circular arrays having respective various structural and functional features.